1. Field of the Invention
The present invention relates to a construction of a regenerator and a regenerative material, which are used as principal components of a regenerative cycle cryocooler (Solvay, Duilleumier, Stirling, Gifford-MacMahon and Pulse tube type) for generating low temperatures in the region between 273K and 2K.
2. Prior Art
The regenerative material for a refrigerator for generating absolute temperatures in the region between 273K and 2K is an essential component for determining the performance of the refrigerator.
Conventionally, in order to manufacture such a regenerative material, a wire net (100 to 500 mesh) of a metal such as copper, bronze or stainless steel, having a high specific heat per unit volume in the operating temperature range is blanked out into a circular shape, and several hundreds of the circular wire nets are packed and laminated in a pipe and used as a regenerative material (hereinafter referred to as a mesh type regenerative material). Alternatively, a regenerative material has been well known which is manufactured by packing innumerable and small (not larger than 0.4 mm in diameter) lead balls, or small balls or fragments of Er3Ni or the like which has a high magnetic specific heat at low temperatures (hereinafter referred to as a small ball type regenerative material).
As described above, the conventional regenerative material is of a mesh type in which several hundreds of circular meshes are laminated, or is of a small ball type in which innumerable and small balls are charged. In the mesh type, however when the meshes are laminated, they are stacked one after another to form a laminate. Therefore, very much time is required to form the laminate by manual operation or machine working using a jig, so that productivity of the laminate is extremely poor.
Also, in the mesh type, since hundreds of meshes are laminated at random, there is a high probability that minute and square fluid path areas of the meshes are blocked up by each other. Therefore, the fluid resistance of working fluid is very high, and thereby, the frictional loss of fluid increases significantly.
Further, in the mesh type, the wire net is mechanically blanked out into a circular form. At this time, shortened fine wires at the circumferential edge of the circular wire net drop out of the net. Therefore, when a regenerator is manufactured by laminating several hundreds of wire nets, the working fluid flows in a large amount through the circumferential edge portion of wire nets, where the fluid resistance is low, resulting in decreased efficiency.
That is, when a regenerator is manufactured by laminating the wire nets in a cylinder, the fluid does not flow at the same velocity in any cross section in the cylinder. The fluid flows in large quantities near the inside wall of the cylinder, which is the circumferential edge of the wire nets, and the flow at the central portion decreases, so that the total heat capacity of wire nets cannot be effectively used, whereby the increase in efficiency is limited.
Also, from the viewpoint of flow resistance and effective use of mesh, there arises a problem that the individual regenerator has different performance if it is manufactured in mass-production. Further, there is a possibility that the shortened fine wires at the circumferential edge are mechanically vibrated by the contact with the high-velocity fluid, and the vibration propagates in the fluid and causes noise at a sensor in a cold head section. On the other hand, the small ball type presents problems that the small ball is crushed and pulverized by mechanical vibration caused by reciprocating motion of a displacer or expansion piston and by a shock wave caused by sudden speed change of fluid, whereby not only the performance of a regenerator is deteriorated but also the pulverized ball intrudes into other components to close the flow path of fluid, causing a system trouble.
The present invention has been made to solve the above problems, and accordingly an object of the present invention is to provide a regenerator having uniform and maintained performance, extremely high productivity and maintained and reliability, and a regenerative material used for the accumulator, so that technical problems in mass production are solved.
In the present invention, the above problems are solved by a mat type regenerative material which is woven into a cloth shape by using: flexible and very long fine wires for longitudinal wire members made of one or a plural kinds of heat storage material having a high specific heat per unit volume in the operating temperature range; and fine wires for transverse wire members each of which comprises a core wire consisting either of a single filament made of at least one kind of ceramic fiber, carbon fiber and synthetic resin fiber having a higher hardness than that of the longitudinal wire member, an appropriate elasticity, and an extremely low heat conductivity, or of a filament composite formed by bundling a number of the single filaments into one body with a fixing agent such as synthetic resin or glass, and polymeric synthetic resin covering the core wire.
Also, the above problems are solved by a mat type regenerative material formed by weaving longitudinal wire members continuously in the lengthwise direction into a cloth shape with transverse wire members as woofs, wherein a transverse wire member is a first fine wire comprising a core wire consisting either of a single filament made of ceramic fiber selected from TYRANO fiber, boron fiber, and zirconia fiber which have an extremely lower heat conductivity than that of the longitudinal wire members, predetermined hardness and elasticity carbon fiber, or other synthetic resin fiber having hardness at least higher than that of the longitudinal wire members or of a filament composite formed by bundling a plurality of the above mentioned single filaments into one body with a fixing agent such as synthetic resin or glass, and a polymeric synthetic resin such as polyimide, polyamide and polyethylene covering outer periphery of the single filament or the filament composite; and a longitudinal wire member is a second fine wire comprising a core wire made of copper, nickel, iron, aluminum, or an alloy thereof having a high specific heat per unit volume in the operating temperature range, whose outer peripheral surface is plated with neodymium, lead or lead alloy and/or covered with fine powder of a material having a high magnetic specific heat, by bonding, joining or coating.
Also, the above problems are solved by a regenerative material characterized in which the diameter (d3) of the transverse wire members is 0.06 to 0.5 mm, and a distance (L1) between the transverse wire members is three to ten times of the diameter of the transverse wire members in order to make the flow resistance of fluid lower than a predetermined value; or the diameter of the transverse wire members (d3) is 0.06 to 0.08 mm, and a third very fine wire members are woven in along the lengthwise direction of the transverse wire member around the longitudinal wire members as cores in order to fix the adjacent longitudinal wire members at a position between the adjacent transverse wire members.
Also, the above problems are solved by a regenerative material in which by heating and compressing the plane of the regenerative material woven into a cloth shape, the polymeric synthetic resin applied to the transverse wire members is deformed along the contact surface with the longitudinal wire members, whereby the longitudinal wire members are fixed and supported on the transverse wire members, and further the aforementioned material having a high magnetic specific heat is formed of at least one kind of material selected from neodymium, DyNi2, Er3Ni, Er6Ni2Sn, and ErNi0.9Co0.1.
Also, the above problems are solved by a regenerator having a construction in which the mat type regenerative material woven into a cloth shape is wound up around a Teflon rod having an extremely low heat conductivity or around a pulse tube of a pulse tube refrigerator to form a regenerator core, and the regenerator core is inserted in a cylindrical member, whereby a working fluid is caused to flow along the lengthwise direction of the transverse wire members.